Correction of negatives



Patented July 26, 1938 UNITED STATES coaaacrron or NEGATIVES William J.Wilkinson, Eastclielt'er, N. Y., assignor of one-half to Miehle PrintingPress and Manufacturing Company, Chicago, 11]., a corporation ofIllinois Application May 11, 1936, Serial No. 79,173

12 Claims.

more different relations.

Referring first to the color-improving procedure, I have heretoforeinvented a method of bettering the color properties of color-separationnegatives by the use of positive film overlays 15 therefor, the filmbeing placed in register over the continuous-separation negative, theuse of the film being essential for the contact method in that the filmmust come as close as possible to the gelatin or emulsion side of theplate to obtain proper dots in the screened positive made by contactwith the separation-negative, but the employment of such corrective filmhas been found to have certain distinct disadvantages.

In this connection, attention is directed to my United States Patent No.2,004,144, Process for photographically producing printing plates,granted June 11, 1935.

The first objectionable feature is that the positive film stretches orshrinks, being subject to atmospheric conditions, and hence making aperfect fit with the negative a matter of substantial difficulty.

A second drawback resides in the thickness of the film which interfereswith the production of a proper dot formation in that its use results inthe making of dots with considerable halo in the shadows and of dots ofmore or less indistinctness in the highlights, these characteristicsbeing due to the refraction of the light caused by the thickness of thefilm and the non-curling coating which is placed thereon by themanufacturers, these two diffusing the beams of light to such an extentas to produce the objectionable feature mentioned.

Various experiments have been resorted to heretofore to substitutesomething diflerent for this film which would eliminate its detrimentalcharacteristics.

The present new method, in so far as it relates to color correction, hasbeen found to eliminate the two objections specified and it consists inthe employment of a much thinner, commercial strip-film which is a verythin light-sensitive emulsion on a paper-backing which, afterdevelopment, is stripped oil! such backing.

While such present commercial strip-films on the market are made withcontrasty emulsions employed for half-tone and line work, yet by amodification of the developer employed this film will make asatisfactory positive overlay for the corrective method, although itwould be preferred to have a strip-film with a more suitable emulsion.

After the corrective positive is made by contact on this strip-film inany appropriate manner, as, for example, is indicated in Patent No.2,004,144, it is stripped off its paper-backing 1 while still wet and itis placed face-down on the emulsion side of the negative to becorrected, the negative preferably having first been previously coatedwith collodion to prevent the negative emulsion from absorbing water.

Such alterative or remedial emulsion positive film is laid in absoluteregister on the negative emulsion and to accomplish this satisfactorilythe film can be stretched, if a trifle too small, and then it issqueegeed in contact with the collodion coating, if that has beenemployed, and the surplus water is eliminated by blotting paper, afterwhich the dual-emulsion is dried.

Due to the fact that this emulsion-film is very thin, yet tough, it ismore easily controlled than the thicker film and hence it may be placedin more accurate and precise register; and, because of its thinness andabsence of non-curling coating, it does not interfere with the lightaction and it produces as good dot formation as a plate without it andalso makes the color-corrective feature as positive as by the oldmethod.

I have also heretofore invented a mask method to eliminate tones fromthe backgrounds of all four color-separation negatives for the purposeof producing pure whites as set forth in my patent application SerialNo. 1,487, filed January 12, 1935.

This procedure involves the production of a set of color-separationnegatives representing the individual colors required conjointly toreproduce the original subject, the making of a positive from one ofsaid negatives, the opaquing on said positive of all tones other thanwhite leaving the areas representing the whites transparent, the makingfrom such opaqued positive a block-out or mask negative in which theareas representing the whites are opaque and all other areas aretransparent, the superimposing of said block-out negative or mask inturn on and in register with each of the color-separation negatives, andmaking a set of white-corrected colorseparation half-tone positives bylight transmitted through each of said negatives in turn and a half-tonescreen or other suitable screen, each of such negatives having said maskin register therewith during the making of its corresponding positive.

Such mask heretofore employed was placed on the glass side of thenegative and then used again for the next negative until it had beenapplied on all four of the negatives to be used.

' In such employment it was placed in register with the negatives by theuse of the existing register marks, but because of the fact that thishas been done on the glass side of the negatives, the thickness of theglass has prevented an absolutely accurate register.

I have now found that each of these negatives can first be coated with acollodion over its emulsion which makes it waterproof and then coatedover the collodion layer with a bichromated glue solution, after whichit is exposed to light through the painted-in or opaqued positive mask.

Each such plate or print is now developed in the usual way by water anddyed in methyl violet solution in the same manner as a copper print forphoto-engraving is dyed, which permits the extent of development to bemade apparent but which does not modify the light-transmittingproperties of the negative.

After having been thus dyed, each such negative is coated with asaturated solution of iodine and potassium bromide, which turns thefilm, where it has been exposed to light, a deep brown color and makessuch portions photographically opaque.

All of these operations are performed on the gelatin side of thenegative and hence the mask is in more perfect register and sharper thanhas heretofore been customary, the mask not being objectionable to themaking of a contact positive as the thinness of the coating so obtaineddoes not interfere with the dot formation.

This mask may 'be used alone on the negative, or a corrective filmoverlay such as described above may be applied to the negative over themask, or the overlay may be applied to the negative and the maskprovided over the overlay.

The separating or intervening collodion coatings may be used betweeneach two of the three layers or one may be employed between any two, orsuch collodion coatings may be dispensed with, but it should beunderstood that in case the overlay or mask is applied directly to thegelatine negative, or to one another without such intervening collodionstratum, subsequent removal of the superposed corrective positive ormask would probably be precluded.

From what precedes it will be apparent that the overlay and mask may 'beapplied to the negative stratum in any order, that either may beomitted, and that the waterproof collodion coatings may or may not beused as preferred, the chosen procedure, however, comprising the use ofboth the overlay and mask, the former correcting the negative as tocolor and the latter assuring pure whites.

The invention, as defined by the following claims, is susceptible of theincorporation of changes in the methods followed and in the resultsproduced all without departure from the underlying principles on whichthe invention is based and without the sacrifice of any of its materialadvantages.

I claim:

1. A corrected negative of a subject consisting of atransparent-support, a negative-stratum of the subject on said support,a corrective-transparency stratum only of the subject and anegative-mask stratum only of the subject superposed in either order onand in register with said negative-stratum and with one another, allthree strata being in adhered relation to one another, said mask beingsubstantially-opaque for all white portions of the subject and otherwisetransparent.

2. A corrected negative of a subject consisting of atransparent-support, a negative-stratum of the subject on said support,a waterproof-coating over said negative-stratum, acorrective-transparency stratum only of the subject and a negative-maskstratum only of the subject superposed in either order on saidwaterproof-coating and in register with said negative-stratum and withone another, and a waterproof-coating between said transparency and maskstrata, all strata and waterproof-coatings being in adhered relation toone another, said mask being substantiallyopaque for all white portionsof the subject and otherwise transparent.

3. In the process of correcting a negativestratum of a subject on atransparent-support, the steps of making a corrective-transparencystratum only of the subject, applying said corrective-transparencystratum on and in register with said negative-stratum, making a mask ofthe subject on and in register with said negativestratum and in whichmask the whites of the subject are substantially opaque and all otherareas transparent, said negative-stratiun being supplied with saidregistering corrective-transparency stratum and said mask in any order,said corrective-stratum and said mask being without support other thansaid negative-stratum and its support.

4. In the process of correcting a negativestratum of a subject on atransparent-support, the steps of making a corrective-positive on alight-sensitive emulsion on a backing, stripping said positive from saidbacking, superposing said corrective-positive stratum on thenegativestratum on said support in adhered and registered relation withsaid negative-stratum, coating said corrective-stratum with alight-sensitive medium, exposing said coating to light through apositivemask of the subject and in which mask all tones other than whiteare substantially opaque and all whites are transparent, and developingsaid exposed coating and rendering said light-exposed areas of saidcoating opaque.

5. The process set forth in claim 4 in which said coating is abichromated-glue solution.

6. In the process of correcting a negativestratum of a subject on atransparent-support, the steps of coating said negative-stratum with alight-sensitive medium, exposing said coating to light through apositive-mask of the subject and in which mask all tones other thanwhite are substantially opaque and all whites are transparent,developing said exposed coating and rendering said light-exposed areasof said coating opaque, making a corrective-positive of the subject on alight-sensitive medium on a backing, stripping said positive from saidbacking, and superimposing said corrective-positive stratum on said maskin adhered and registered relation with said negativestratum and mask.

7. In the process of correcting a negativestratum of a subject on atransparent-support, the steps of coating said negative-stratum with abichromated-glue solution, exposing said coating to light through apositive-mask of the subject and in which mask all tones other thanwhite are substantially opaque and all whites are transparent,developing said exposed coating and rendering said light-exposed areasof said coating opaque, making a corrective-positive of the subject on alight-sensitive emulsion on a backing, Stripping said positive from saidbacking, and superimposing said corrective-positive stratum on said maskin adhered and registered relation with said negative-stratum and mask.

8. In the process of correcting a negativestratum of a subject on atransparent-support, the steps of coating said negative-stratum with awaterproof material, making a corrective-positive of the subject on alight-sensitive emulsion on a backing, stripping said positive from saidbacking, superimposing said corrective-positive stratum on saidwaterproof-coating in adhered and registered relationwithsaidnegative-stratum, coating said corrective-stratum with awaterproof material, coating said second waterproofcoating with alight-sensitive medium, exposing said light-sensitive coating to lightthrough a positive-mask of the subject in which all tones other thanwhite are substantially opaque and all whites are transparent, anddeveloping said exposed coating and rendering said light-exposed areasof said second coating opaque.

9. The process set forth in claim 8 in which said light-sensitive mediumis a bichromatedglue solution.

10. In the process of-correctlng a negativestratum of a subject on atransparent-support, the steps of applying a waterproof-coating to saidnegative-stratum, coating said waterproof-coating with a light-sensitivemedium, exposing said light-sensitive coating to light through apositive-mask of the subject and in which mask all tones other thanwhite are substantially opaque and all whites are transparent,developing said exposed coating and rendering the light-exposed to themultiple-strata prior to supplying said multiple-strata with its finallayer.

12. A corrected negative of a subject including a transparent-support, anegative-stratum of the subject on said support, acorrective-transparency stratum only of the subject and a negative maskstratum only of the subject superposed in either order on and inregister with said negative-stratum and with one another, said maskbeing substantially-opaque for all white portions of the subject andotherwise substantially-transparent, and a waterproof-coating stratumbetween at least two of said strata, all strata being in adheredrelation to one another.

WILLIAM J. WILKINSO

